Creating a Coincidence Constraint

	Coincidence-type constraints are used to align elements.
	Depending on the selected elements, you may obtain concentricity, coaxiality or coplanarity. The tolerance i.e. the smallest distance that can be used to differentiate two elements is set at 10 -3 millimeters.
	The following table shows the elements you can select.

	Point	Line	Plane	Planar Face	Sphere (point)	Cylinder (axis)
Point
Line
Plane
Planar Face
Sphere (point)
Cylinder (axis)

This task consists in applying a constraint between two faces.

Before constraining the desired components, make sure it belongs to a component defined as active (the active component is blue-framed and underlined).

Open the Constraint1.CATProduct document.

Click the Coincidence Constraint icon

This command is also available from the Insertmenu.

Select the face to be constrained, that is the red face as shown.

Select the second face to be constrained, that is the blue circular face in the direction opposite to the red face.

Green arrows appear on the selected faces, indicating orientations.

The Constraint Properties dialog box that appears displays the properties of the constraint. The components involved and their status are indicated. You can define the orientation of the faces to be constrained by choosing one of these options:

	Undefined (the application finds the best solution)
	Same
	Opposite

Note that when changing a 'Same' orientation into an 'Opposite' orientation or vice-versa, the application may sometimes positions the parts in an unexpected way especially if your system is under-constrained.

For the purposes of our scenario, set the Opposite option.

Click OK to create the coincidence constraint.

As the coincidence constraint is created, the red component is moved so as to adopt its new position. Green graphic symbols are displayed in the geometry area to indicate that this constraint has been defined.

This constraint is added to the specification tree too.

Graphic symbols used for constraints can be customized. For more information, refer to Customizing Constraint Appearance.